The present invention is concerned with a retractable cover apparatus for an open-topped container such as a truck or trailer bed, and is particularly concerned with a cable drive assembly for operating the apparatus.
Conventional truck and truck trailer bodies used in the transport of various materials such as sand, gravel, grain, or other loose material are of open frame construction with a base, upstanding side and end walls, and an open top. Clearly, the open top of such containers poses problems, since wind may blow material from the top of the truck, potentially causing a driving hazard, and produces wind resistance and drag on the truck movement.
In view of these problems, such open topped containers are often covered with a tarpaulin so as to protect the cargo and reduce drag. In some cases, a tarpaulin is wound on a roller at one end of the container opening, and is pulled out manually over the load before being tied down. On arrival at the load destination, the tarpaulin is released and wound back onto the roller by a spring. This approach requires considerable manual effort in deploying and tying down the tarpaulin, and potentially causes risk to the operator. Also, if the cover is not properly tied down, it will tend to lift off the trailer at high speeds, potentially tearing away and causing a hazard to the truck driver and others.
Cable operated cover systems are known, in which a cover is attached at one end to an end of the container opening, and at the other end to endless cables extending along the sides of the container or trailer bed. The cables extend around sheaves or pulleys. A reversible electric motor or hand crank drives a sprocket, which in turn rotates a sheave around which the cable extends. Some such systems have separate endless cables along opposite sides of the truck or trailer bed, but this can cause jamming of the front end of the tarpaulin if the two cables are not precisely matched. A system of this type is described, for example, in U.S. Pat. No. 5,253,914 of Biancale.
The single cable top slider system manufactured by Pulltarps Mfg. of San Diego, Calif., avoids such problems by attaching the front end of the tarpaulin to the same cable on both sides. In this system, an endless cable extends around guide pulleys to travel in a path along one side of the open container, one end of the container, the opposite side of the container, and then back along the same path to complete the loop. Thus, movement of the cable causes cooperative movement of opposite sides of the tarpaulin. Another single cable drive system is described in U.S. Pat. No. 5,145,230 of Biancale. In each case, a suitable hand or motor driven winch is provided for driving the cable. One problem with such systems is the difficulty in mounting them on the truck bed or trailer. Each of the pulleys, the winch, and the drive motor, must be mounted separately and in proper alignment. Another problem is potential cable slipping on the winch, jamming the tarpaulin movement.
It is an object of the present invention to provide a new and improved retractable tarpaulin cover apparatus and cable drive assembly therefor.
According to one aspect of the present invention, a cover apparatus for an open-topped container such as a trailer or truck bed is provided, which comprises a cover for extending over the open top of a container, the cover having opposite sides, a plurality of spaced, parallel bows extending between opposite sides of the cover, each bow having a guide at each end; an endless cable running through the guides at each end of each bow, a rear one of the bows being secured to the cable and the guides on the remaining bows engaging slidably on the cable; a plurality of support pulleys for supporting the cable to extend in a predetermined path along the opposite sides of the container; and la pair of meshing gear drive pulleys for controlling movement of the cable to extend and retract the cover, a reversible drive motor linked to one of the gear drive pulleys, and the cable extending at least partially around each of the gear drive pulleys.
In one embodiment, the gear drive pulleys each have at least one cable receiving groove and a series of gear teeth meshing with the teeth of the other drive pulley, reducing or eliminating the risk of cable slipping. An adjustable tensioning pulley may be provided for adjusting cable tension, and a first one of the gear drive pulleys may have two spaced cable grooves, with the cable passing around one of the grooves in the first drive pulley, around the groove in the second drive pulley , then around the tensioning pulley, and back around the other groove in the first drive pulley. The tensioning pulley may be positioned at a selected spacing from the gear drive pulleys in order to provide the desired cable tension for proper operation of the drive assembly.
In one embodiment of the invention, an elongate housing having opposite first and second ends is provided for mounting at one end of a container to be covered, the housing having a cable access opening at each end. Some of the support pulleys as well as the motor and gear drive pulleys are mounted in the housing. This makes the retractable cover assembly much easier to install on a truck or trailer bed. The housing may have an upper, aerodynamically shaped wall to which one end of the cover is secured, with the wall suitably aligned to form a smooth, aerodynamic shape between the wall and next adjacent bow of the cover. This avoids the problem of a flat region of the cover, which previously arose when a cover was simply secured flat to one end of container opening, and could give rise to wind drag. The enclosure is suitably waterproof to reduce the risk of damage to the motor or gear drive pulleys in inclement weather conditions or due to wind pressures when the truck is driven at high speeds.
The arrangement of meshing gear drive pulleys provides a considerable improvement in operation of the retractable cover, helping to overcome any jam or cable slipping. The provision of a self-contained housing for the motor, gear drive pulleys, and all of the support pulleys at one end of the container makes the original mounting of the apparatus on a truck or trailer bed much easier. It also provides a streamlined shape at the end of the cover, reducing wind drag so that there is less risk of the cover becoming detached or tearing away. The housing will,protect the drive assembly from damage, increasing the system lifetime.